Yesterday I received one of those "healthy living" magazines from a local hospital. It contained an article about rehydrating after exercise. The doctor is quoted as saying, "Follow a regular fluid regiment." Because the writer or the doctor (or both) chose the wrong word of a similar word pair, the sentence doesn't make sense.
A regiment is a military unit of two or more battalions. However, a regimen is a specially prescribed course, usually related to diet or exercise. And a regime is the government in power.
The embarrassment potential for misusing these words is high because many people know the difference between regimen and the other two. If you're confronted with a troublesome word pair or triplet, your best friend is a dictionary. These three words--regime, regimen, and regiment--follow each other, so it's easy to check which one to use.